Advanced Humid Air Gas Turbine System

ABSTRACT

One of the objects of the invention is to provide a water-saving type advanced humid air gas turbine system (AHAT) that can decrease the amount of makeup water to be supplied from the outside, by reducing the amount of water consumed when the gas turbine system is starting up, shut down, or subjected to load rejection. 
     The AHAT includes a gas turbine system; a heat recovery steam generator for generating steam by use of exhaust gas from a turbine; a water recovery system for recovering moisture contained in the exhaust gas; a first steam system for supplying steam, coming from the heat recovery steam generator, to a compressed air header; and a second steam system for supplying steam, coming from the heat recovery steam generator, to the heat recovery steam generator or the water recovery system. The gas turbine system includes a compressor, the compressed air header for generating humidified combustion air, a combustor for generating combustion gas, and the turbine. When the gas turbine system is starting up, shut down or subjected to load rejection, steam coming from the heat recovery steam generator is recovered by blocking the first steam system and making the second steam system communicate with the heat recovery steam generator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to advanced humid air gasturbine systems. Specifically, the invention relates to an advancedhumid air gas turbine system that recovers moisture from exhaust gasafter combustion and recycles it as humid air.

2. Description of the Related Art

In the operation of a gas turbine system, it is widely known in the artthat steam is introduced into compressed air for combustion in order toimprove power generation efficiency. This is because the introduction ofsteam increases the amount of working fluid, i.e., the compressed airfor combustion to reduce the power necessary for a compressor to work.

The advanced humid air gas turbine system (hereinafter, referred to asAHAT) exemplified in JP-2010-255456-A is configured as follows. Steamintroduced into a gas turbine from exhaust gas after combustion iscondensed and recovered as recovered water. Impurities are removed fromthe recovered water with the use of an impurity removing device. Suchrecovered water is used to humidify the compressed air for combustion tobe turned into humid compressed air for combustion. This system allowsthe heat present in the exhaust gas after combustion to be recovered tothe inlet side of the combustor, which in turn raises the temperature ofthe compressed air for combustion. The system further improves the powergeneration efficiency as a result of the reduction in the fuelconsumption.

SUMMARY OF THE INVENTION

The AHAT includes a water recovery system for recovering moisture fromthe exhaust gas of the gas turbine and a superheated steam generationsystem for generating superheated steam in the heat recovery steamgenerator that uses the exhaust gas of the gas turbine as a heat source.The superheated steam generated in the superheated steam generationsystem is introduced into the compressed air for combustion in the gasturbine.

Incidentally, in the operation of the gas turbine, superheated steam isnot introduced into compressed air for combustion in order to preventmoisture from being condensed in the gas turbine at the time of start-upand shut-down. Also in the case of operation after load rejection hasbeen carried out due to a system failure or the like during theoperation of the gas turbine system, superheated steam is not introducedinto compressed air for combustion.

If such a gas turbine cannot introduce superheated steam, theconventional AHAT is operated such that the superheated steam generatedat a relief valve installed at the outlet of the hear recovery steamgenerator is discharged to the outside of the system.

When the AHAT is operated with DSS (Daily Start and Stop) cycles or ittakes a long period of time until resynchronization after the loadrejection, the amount of consumed water will increase. The increasedamount of makeup water results in a rising running cost.

The present invention has been made in view of above-mentionedsituations and aims to provide a water-saving type advanced humid airgas turbine system that can reduce the amount of makeup water to besupplied from the outside by reducing the amount of consumed water whenthe gas turbine system is starting up, shut down or subjected to loadrejection.

To solve the foregoing problems, an aspect of the present inventionincorporates, for example, the arrangements of the appended claims. Thisapplication includes a plurality of means for solving the problems. Anexemplary aspect of the present invention provides an advanced humid airgas turbine system (AHAT) including: a gas turbine system; a heatrecovery steam generator for generating steam by use of exhaust gas froma turbine; a water recovery system disposed on the downstream side ofthe heat recovery steam generator, the water recovery system recoveringmoisture contained in the exhaust gas; a first steam system forsupplying steam, coming from the heat recovery steam generator, to acompressed air header; and a second steam system for supplying steam,coming from the heat recovery steam generator, to the heat recoverysteam generator or the water recovery system. The gas turbine systemincludes a compressor for compressing air, the compressed air header formixing high-pressure air introduced from the compressor with steam so asto generate humidified combustion air, a combustor for mixing thecombustion air from the compressed air header with fuel for sake ofcombustion so as to generate combustion gas, and the turbine driven bythe combustion gas that is generated by the combustor. When the gasturbine system is starting up, shut down or subjected to load rejection,steam coming from the heat recovery steam generator is recovered byblocking the first steam system and making the second steam systemcommunicate with the heat recovery steam generator.

According to the present invention, the bypass system which bypasses thegas turbine and leads the generated steam into the system of theadvanced humid air gas turbine system is installed at the steam outletof the heat recovery steam generator. The amount of water consumed whenthe gas turbine is starting up, shut down, or subjected to loadrejection can be reduced. The amount of makeup water to be supplied fromthe outside when the gas turbine is starting up, shut down, or subjectedto load rejection can be reduced. Thus, a reduction in starting up costcan be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration diagram illustrating a firstembodiment of an AHAT of the present invention;

FIG. 2 is a schematic configuration diagram illustrating a secondembodiment of an AHAT of the present invention; and

FIG. 3 is a schematic configuration diagram illustrating a thirdembodiment of an AHAT of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of an AHAT of the present invention willhereinafter be described with reference to the drawings.

First Embodiment

FIG. 1 is a schematic configuration diagram illustrating a firstembodiment of the AHAT of the present invention.

The AHAT includes a gas turbine system, a heat recovery steam generator10 and a water recovery system 6 as a basic configuration. The gasturbine system includes a compressor 1, a compressed air header 2, acombustor 3, a turbine 4, a drive shaft 1A, and a generator 5. Thecompressor 1, the turbine 4, and the generator 5 are mechanicallyconnected to one another by means of the drive shaft 1A.

The compressor 1 sucks and compresses outside air and supplies thecompressed air as combustion air to the compressed air header 2 via aflow passage 51. The compressed air header 2 mixes superheated steamwith the combustion air to generate humidified combustion air. Thesuperheated steam is supplied from a superheater 14 of the heat recoverysteam generator 10 via a pipe 52 and a pipe 55 to the compressed airheader 2. The combustor 3 mixes the humidified combustion air suppliedthereto via a flow passage 53 with fuel F supplied thereto via a pipe 50for combustion to generate high-temperature and high-pressure combustiongas. This combustion gas is introduced via a flow passage 54 to theturbine 4 to drive the turbine 4, thereby driving the compressor 1 andthe generator 5 via the drive shaft 1A. The rotary power of the turbine4 is converted into electricity by the generator 5.

The heat recovery steam generator 10 is equipment that uses, as a heatsource, exhaust gas that has driven the turbine 4 in the gas turbinesystem to generate steam. The heat recovery steam generator 10 includesa box-shaped casing 10 a which covers its outer circumferential portionwith a lagging material; an upstream opening portion provided on theupstream side of the casing 10 a and connected to a duct 60 adapted tointroduce exhaust gas that has driven the turbine 4; an exhaust gaspassage through which the exhaust gas introduced from the upstreamopening portion flows; a heat exchanger group; and a downstream openingportion provided on the downstream side of the casing 10 a and adaptedto supply the exhaust gas having passed through the heat exchanger groupto a water recover system 6. The heat exchanger group is composed of thesuperheater 14, an evaporator 13 equipped with a steam drum 31, ahigh-temperature economizer 12 and a low-temperature economizer 11,which are arranged in this order from the upstream in the exhaust gaspassage.

In the present embodiment, a steam nozzle 15 for jetting superheatedsteam in the direction of the exhaust gas passage is provided on theupstream side of the superheater 14 in the exhaust gas passage of theheat recovery steam generator 10. A pipe 58 is connected at one endthereof to the header of the steam nozzle 15. The pipe 58 has the otherend coupled to a branch portion 56 provided on the pipe 55 connectingthe heater 14 of the heat recovery steam generator 10 to the compressedair header 2. A steam nozzle adjusting valve 91 and an orifice 100 areprovided on the pipe 58, the steam nozzle adjusting valve 91 beingadapted to adjust the flow rate of superheated steam supplied to thesteam nozzle 15. The steam nozzle adjusting valve 91 is closed duringnormal operation.

In the present embodiment, the lower structure of the casing 10 acorresponding to the bottom of the heat recovery steam generator 10 isdesigned as an inclined structure 16 where the inclination descends fromthe upstream side toward the downstream side. A pipe 82 is provided at aminimum height portion on the most-downstream side of the inclinedstructure 16. This pipe 82 is made to communicate with a drain tank 32for storing drain. The drain stored in the drain tank 32 is dischargedto the outside of the AHAT by means of a pipe 83 arranged to extendtoward the outside thereof, and a drain pump 41 installed on the pipe83.

The water recovery system 6 sprays cooling water from a spray nozzle 120to the exhaust gas from the heat recovery steam generator 10 to condensethe moisture in the exhaust gas into water. The water recovery system 6mixes such water with cooling water and recovers the mixture as recoverywater 20. The remaining gas component resulting from removing themoisture from the exhaust gas is discharged to the atmosphere from afunnel 110 provided on the upper portion of the water recovery system 6.As the cooling water to be sprayed from the spray nozzle 120, therecovery water 20 is used that is supplied from the lower portion of thewater recovery system 6 via a pipe 81 to an outside cooler (not shown)in which the water is cooled. The recovery water 20 supplied to theoutside cooler for cooling may be purified with a water processingdevice (not shown) and the purified water may be reused as the feedwater of the exhaust recovery boiler 10.

During the normal operation of the gas turbine system, the exhaust gashaving driven the turbine 4 is supplied via the duct 60 to the heatrecovery steam generator 10 before being subjected to heat exchange withthe feed water or steam flowing inside the above-mentioned heatexchanger group. The superheated steam, generated from the superheater14 due to such heat exchange, after passing through the pipe 55connecting the superheater 14 to a superheated steam adjusting valve 90,is supplied to the compressed air header 2 via the superheated steamadjusting valve 90 and the pipe 52. The superheated steam adjustingvalve 90 reduces the pressure inside the superheated steam to a pressurenecessary for the gas turbine system to work. As a result, humidifiedair to be supplied to the combustor 3 is generated.

Moreover, during the normal operation of the gas turbine system, wateris supplied from the outside via a pipe 70 to the low-temperatureeconomizer 11. This water is subjected to heat exchange in thelow-temperature economizer 11 and is then supplied via a pipe 74 to adeaerator 30 for deaeration of the water. Thereafter, such water passesthrough a pipe 73 and is increased in pressure at a feed-water pump 40.Then, the water is supplied via a pipe 72 to the high-temperatureeconomizer 12, in which the water is subjected to heat exchange. Thewater leaving the high-temperature economizer 12 is supplied to thesteam drum 31 via a pipe 78 and a pipe 76.

The water supplied to the steam drum 31 is circulated and heated throughthe evaporator 13, a pipe 79, and a pipe 80. Water and steam areseparated from each other in the steam drum 31. The steam is suppliedvia a pipe 57 to the superheater 14. The steam supplied to thesuperheater 14 is further heated to be turned into superheated steam,which is supplied to the pipe 55.

A description will now be given of how the gas turbine system in thepresent embodiment is operated at the time of starting up and shut-down.

When moisture is prevented from being condensed in the gas turbine, suchas when the gas turbine system is starting up or shut down, and whensteam is not needed as after load rejection, a steam nozzle adjustingvalve 91 is operatively opened and, at the same time, a superheatedsteam adjusting valve 90 is operatively closed first. In this way,superheated steam, led to the pipe 58, is jetted from the steam nozzle15 toward the direction of the exhaust gas passage of the heat recoverysteam generator 10. In addition, the inflow of the superheated steamtoward the gas turbine is blocked.

The superheated steam jetted from the steam nozzle 15 toward thedirection of the exhaust gas passage of the heat recovery steamgenerator 10 could be drained after being condensed with thehigh-temperature economizer 12 or the low-temperature economizer 13 inthe heat recovery steam generator 10 in some cases. Such drain passesthrough the inclined structure 16 of the lower portion of the casing 10a of the heat recovery steam generator 10, goes through the minimumheight portion on the most-downstream side and is stored in the draintank 32. Then, the drain is discharged by the drain pump 41 to theoutside of the system of the AHAT.

According to the first embodiment of the AHAT of the present inventiondescribed above, the bypass system is installed at the steam outlet ofthe heat recovery steam generator 10. The bypass system bypasses the gasturbine and leads the generated steam into the inside of the system ofthe AHAT. Therefore, the amount of water consumed when the gas turbineis starting up, shut down, or subjected to load rejection can bereduced. As a result, the amount of makeup water to be supplied from theoutside when the gas turbine is starting up, shut down, or subjected toload rejection can be reduced. Therefore, a reduction in starting upcost can be achieved.

The present embodiment describes as an example the case where the steamnozzle 15 is installed on the most-upstream side of the exhaust gaspassage of heat recovery steam generator 10. However, the presentinvention is not limited to this. The steam nozzle 15 can also bedisposed on areas where the following conditions are met: the exhaustgas temperature in the exhaust gas passage of the heat recovery steamgenerator 10 is higher than saturated temperature corresponding to theinner pressure of the steam drum 31; and water condensation does notoccur at the installation portion of the exhaust nozzle 15. Theseconditions are in order to avoid the problem such as a thermal shock.For example, a configuration is available in which the steam nozzle 15is installed between the evaporator 13 and the superheater 14. Anotherpossible configuration is that in which the evaporator 13 is dividedinto two evaporators and the steam nozzle 15 is installed between suchtwo evaporators 13.

The present embodiment describes as an example the case where the draindischarge system including the drain pipe 82, the drain tank 32, and thedrain pump 41 is provided to discharge the drain in the heat recoverysteam generator 10. However, the present invention is not limited tothis. The present embodiment may be configured such that drain candirectly be discharged from the inclined structure 16 to the waterrecovery system 6. In this way, the drain discharge system can beomitted.

Second Embodiment

A second embodiment of an AHAT according to the present invention ishereinafter described with reference to the drawings. FIG. 2 is aschematic configuration diagram illustrating a second embodiment of theAHAT of the present invention. In FIG. 2, the same reference numerals asthose in FIG. 1 denote like portions and their detailed explanations arethus omitted.

The AHAT according to the second embodiment of the present inventionshown in FIG. 2 is composed of almost the same devices as those in thefirst embodiment but is different from that of the first embodiment inthe following configuration. In the present embodiment, the steam nozzle15 is installed inside the water recovery system 6. The drain exhaustsystem including the drain pipe 82, the drain tank 32, and the drainpump 41 is omitted. The lower portion of the casing 10 a of the heatrecovery steam generator 10 is configured not to have the inclinedstructure but to have a flat structure.

In the second embodiment of the AHAT, when moisture is prevented frombeing condensed in the gas turbine, such as when the gas turbine systemis starting up or shut down, and when steam is not needed as after loadrejection, a steam nozzle adjusting valve 91 is operatively opened and,at the same time, a superheated steam adjusting valve 90 is operativelyclosed first. As a result, superheated steam, led to the pipe 58, isjetted from the steam nozzle 15 toward the inside of the water recoverysystem 6. In addition, the inflow of the superheated steam toward thegas turbine is blocked. The superheated steam jetted into the waterrecovery system 6 is condensed into recovery water 20 by use of thecooling water jetted from a spray nozzle 120. The recovery water 20 isrecovered into the system of the AHAT.

Incidentally, the superheated steam jetted from the steam nozzle 15 isof a high temperature, which deviates from the temperature conditionsinside the water recovery system 6. However, the steam nozzle 15 isarranged so as not to come into direct contact with members constitutingthe water recovery system 6. Thus, the water recovery system 6 can bedesigned on the basis of normal operational specifications.

The second embodiment of the AHAT of the present invention describedabove can produce the same advantages as those of the first embodiment.

According to the second embodiment of the AHAT of the present invention,drain is unlikely to occur in the heat recovery steam generator 10. Itis not necessary to install the drain discharge system and to configurethe lower portion of the casing 10 a of the heat recovery steamgenerator 10 as the inclined structure. Accordingly, production costscan be reduced.

Third Embodiment

A third embodiment of an AHAT according to the present invention willhereinafter be described with reference to the drawings. FIG. 3 is aschematic configuration diagram illustrating the third embodiment of theAHAT of the present invention. In FIG. 3, the same reference numerals asthose in FIG. 1 denote like portions and their detailed explanations arethus omitted.

The AHAT according to the third embodiment of the present inventionshown in FIG. 3 is composed of almost the same devices as those in thefirst embodiment but is different from that of the first embodiment inthe following configuration. The pipe 58 is connected at one end thereofto the branch portion 56 of the pipe 55 and at the other end to thecooler of the gas turbine system. The drain exhaust system including thedrain pipe 82, the drain tank 32, and the drain pump 41 is omitted. Thelower portion of the casing 10 a of the heat recovery steam generator 10is configured so as not to have the inclined structure but to have aflat structure.

In the third embodiment of the AHAT, when moisture is prevented frombeing condensed in the gas turbine, such as when the gas turbine systemis starting up or shut down, and when steam is not needed as after loadrejection, a steam nozzle adjusting valve 91 is operatively opened and,at the same time, a superheated steam adjusting valve 90 is operativelyclosed first. As a result, superheated steam is led to the pipe 58 andthe inflow of the superheated steam toward the gas turbine is blocked.The superheated steam led to the pipe 58 is condensed for reuse by useof the cooler located on the outside of the system of the AHAT.

The third embodiment of the AHAT of the present invention describedabove can produce the same advantages as those of the first embodiment.

1. An advanced humid air gas turbine system comprising: a gas turbinesystem that includes a compressor for compressing air, a compressed airheader for mixing high-pressure air introduced from the compressor withsteam to generate humidified combustion air, a combustor for mixingcombustion air from the compressed air header with fuel for sake ofcombustion so as to generate combustion gas, and a turbine driven by thecombustion gas that is generated by the combustor; a heat recovery steamgenerator for generating steam by use of exhaust gas from the turbine; awater recovery system disposed on a downstream side of the heat recoverysteam generator, the water recovery system recovering moisture containedin the exhaust gas; a first steam system for supplying steam, comingfrom the heat recovery steam generator, to the compressed air header;and a second steam system for supplying steam, coming from the heatrecovery steam generator, to the heat recovery steam generator or thewater recovery system, wherein when the gas turbine system is startingup, shut down, or subjected to load rejection, steam coming from theheat recovery steam generator is recovered by blocking the first steamsystem and making the second steam system communicate with the heatrecovery steam generator.
 2. The advanced humid air gas turbine systemaccording to claim 1, wherein the second steam system is coupled to asteam nozzle for jetting steam into an exhaust gas passage of the heatrecovery steam generator.
 3. The advanced humid air gas turbine systemaccording to claim 1, wherein the heat recovery steam generator has abox-shaped casing, the casing having at a bottom portion thereof aninclined structure where inclination descends from upstream side towarddownstream side of a flow of exhaust gas from the turbine, and wherein adrain exhaust system is provided at a most-downstream-side portion ofthe bottom portion of the casing.
 4. The advanced humid air gas turbinesystem according to claim 1, wherein the second steam system isconnected to a steam nozzle for jetting steam toward an inside of thewater recovery system.
 5. The advanced humid air gas turbine systemaccording to claim 1, wherein the second steam system is connected to acooler located outside the advanced humid air gas turbine system.